The present invention relates to a method of detecting and correcting a direction of image data and more particularly to a method of detecting and correcting a direction of a document image and a system employing the same which are suitable for being applied to an image filing system with an automatic document feeder.
In recent years, an image filing system is out in the market as the fourth office automation system following a word processor, a personal computer and a facsimile, and is attracting much attention as means for pursuing the paperless promotion in a class of an office or design. The image filing system is designed in such a way as to accumulate a large quantity of image information by utilizing an optical disc and to read out the image information therefrom promptly according to need to print them. Therefore, the image filing system is caused to be remarkably used by the class generating a large quantity of documents. As a result, it becomes one of important problems in the image filing system to promote the labor-saving of the work of inputting documents and drawings generated in large quantities every day.
With respect to the work of inputting an image, the prior art image filing system is provided with an automatic document feeder for automatically feeding an input document to promote automation of the input work. As for the image filing system with an automatic document feeder, there is known an optical disc Filing System, e.g., Hitachi 650EX manufactured by Hitachi, Ltd.
However, in such systems, since the direction of scanning an image is made to be uniform by a direction from the top to the bottom, there is needed a great deal of work in the processes before and after the automatic document feeding. That is, in the process prior to the automation document feeding, an operator needs to carefully arrange the document in one direction. Moreover, in the process posterior thereto, the inputted images need to be displayed one by one to confirm the direction of the document.
Hitherto, as a system for solving the above-mentioned disadvantages, there is given JP-A-2-79184 which was filed with the Patent Office of Japan by the present patent applicant and was laid open to public inspection on Mar. 19, 1990.
In this prior art, the discrimination of the input direction is achieved in such a way that a predetermined amount of rotation is given to the input image itself and characters included in the image having the rotation thus given thereto are recognized. Moreover, in this prior art, if the correction is given to the proper direction, it is possible to achieve automatic correction of the input image.
More specifically, image data outputted from image input means or storage means are rotated in the forward or reverse direction every predetermined angle, and the processing of recognizing the image data which has been subjected to the rotation processing is performed every rotation to judge the image data having a high recognition rate to be in a direction of a normal image.
As described above, the system employing that prior art is designed in such a way that the rotation is given to the input or output image data themselves, and the characters included in the image data thus rotated are recognized to obtain the direction of the input or output image. Therefore, the arrangement of the direction of the document and the visual inspection of the input image which must be performed even using the scanner with an automatic document feeder become needless. As a result, it is possible to improve the registration speed of the image data.
As described above, according the above-mentioned prior art, the arrangement of the direction of the input document and the visual inspection for confirmation of the image become needless. As a result, the problem relating to the labor-saving in the input work is largely improved.
However, in the above-mentioned prior art, since the rotation is given to the input image itself, there still remains a problem in which the time required for the detection processing is increased.
More specifically, a document of a standard A4 size has a quantity of data of 500 KB or so, and therefore, even if such a document is processed using an exclusive image processor, a time from a several seconds to several tens of seconds is required. Accordingly, although the above-mentioned prior art attains the object of automation free from labor, there is provided a disadvantage in which work efficiency is reduced as compared with the case requiring the labor. Incidentally, "A4" is one size of a business recording sheet which is standardized by the Japanese Industry Standard. Moreover, in the above-mentioned prior art, it is suggested that a character recognition dictionary used for recognizing an inversion character or the like is used. However, the capacity of the character recognition dictionary is obliged to be unnecessarily large.
Incidentally, as for the related application in the image filing system by the present patent applicant, there are known "Method And Apparatus For Rotating Dot's Data" by K. Okazawa et al., U.S. patent application Ser. No. 271,275 issued as U.S. Pat. No. 5,034,733. In these articles, there is disclosed a technique of rotating image data.